Generally, the liquid crystal display device which has features of a light weight, a thin shape, and low power consumption is used as a display device. The liquid crystal display device is equipped with an array substrate, a counter substrate arranged opposing the array substrate with a gap therebetween, and a liquid crystal layer held between the array substrate and the counter substrate.
The array substrate includes a glass substrate. In a display region, a plurality of signal lines and a plurality of scanning lines cross on the glass substrate. A Thin Film Transistor (TFT) is arranged near an intersection portion where each of the signal lines crosses each of the scanning lines, and each TFT forms a pixel. Moreover, a driving circuit (Y driver) connected to the plurality of the scanning lines is arranged on the glass substrate.
By the way, in the liquid crystal display device, the demand for high definition and narrow frame is becoming strong. When advancing the features of the high definition and the narrow frame, a large width of the driving circuit results in a problem. The single-sided arrangement of the left-hand side or the right-hand side of the Y driver is common for the liquid crystal display device especially with a small panel size used for cellular phones, digital still cameras, etc.
Moreover, in the above-mentioned liquid crystal display device, the screen size becomes larger, and the number of pixels increases every year. Since the occupied area of the Y driver corresponding to each scanning line is decided beforehand, if the number of pixels increases and a pixel pitch becomes narrow, a layout width of the Y driver with respect to the pixel pitch is expanded relatively. However, when the layout width of the Y driver is expanded, there is a problem that the narrow frame technique can not be advanced.
Then, when the narrow frame technique is advanced, it is possible to arrange the Y driver on the glass substrate by dividing the above-mentioned Y driver on the both sides of the display region. For example, odd scan lines are connected to the left-hand side of the Y driver, and even scanning lines are connected to the right-hand side of the Y driver. Thereby, although the layout of the Y driver for one scanning stage was conventionally arranged at one pixel pitch, it becomes possible to arrange the layout of the Y driver for one scanning stage at two pixel pitches in the above technique. As a result, since the Y driver can take a sufficient layout area even if the width of the Y driver is set to be narrower, the narrow frame is achieved.
However, in the above-mentioned liquid crystal display device, especially in the liquid crystal display device with a large screen size or a high definition characteristics, when a gray raster display is carried out by a line inversion drive (horizontal line inversion drive system) which changes polarity for every line, a flicker on the right-and-left end of the screen is caused.
Here, the causes which generate the flicker are explained. In the scanning lines, one end to which the scanning signals are inputted is set to a starting end, and another end at which the transmitting of the scan signals terminates is set to a terminal end. The waveform is more rounded at the terminal end side compare with the starting end side due to a load of the scanning line. Since a punch-through voltage remarkably depends on the waveform of the scanning signal, the punch-through voltage becomes smaller by the enlargement of the roundness of the waveform at the terminal end side. As a result, the holding potential of the pixel becomes larger at the terminal end side.
At a left end and a right end of the screen, since the starting end and the terminal end of the scanning line are arranged by turns, the pixels with the large punch-through voltage and the pixels with the small punch-through voltage (high or low holding potential in the pixel) are also arranged by turns. Moreover, the holding voltage difference among the pixels due to the difference of the punch-through voltages depends on the polarity of the holding voltage.
For example, in case of a dot inversion drive (HV/horizontal-vertical inversion drive) in which the polarity is changed in each pixel, the pixels of positive polarity and negative polarity are arranged alternately for both of the odd row lines and even row lines for one frame. As a result, the influence by the punch-through voltage of the pixels is balanced for each row line.
On the other hand, in the line inversion drive, since the polarities of the pixels differ in the odd row lines and the even row lines, and further the punch-through voltage is different between the positive polarity pixel and the negative polarity, the influence by the punch-through voltage changes in every row line. When a gray raster display is performed by the line inversion drive, the fault that a flicker occurs at the right-and-left end of the display region arises due to above-mentioned causes.